Effect of the presence of CO₂ on the adsorption of HCHO on activated carbon

Abstract

Activated carbon is a high-quality material for removing indoor pollution, while when people use activated carbon as a purifying material in extreme scenarios such as poorly ventilated underground spaces to remove volatile organic compounds such as formaldehyde (HCHO), it will inevitably be affected by the presence of high concentrations of carbon dioxide (CO₂).To explore the competitive adsorption characteristics of HCHO and CO₂ on activated carbon, the activated carbon model was constructed using Materials Studio software. The simulation of single-component adsorption was conducted using the giant regular Monte Carlo method at different temperatures. The results showed that the amount and heat of adsorption of HCHO and CO₂ decreased with increasing temperature. In 2 nm pore size, the capillary coalescence phenomenon occurred in HCHO and adsorption increased abruptly, while the capillary condensation of HCHO did not occur in other pore sizes. Meanwhile, the competitive adsorption simulation of gas under different partial pressure ratios was further studied. The results showed that the adsorption amount of CO₂ was gradually larger than that of HCHO with the gradual increase of the partial pressure of CO₂. However, when the partial pressure ratio of the two was the same, the interaction force between HCHO and activated carbon was stronger than that of CO₂. In competitive adsorption, the strong adsorbent HCHO competes with the adsorbed CO₂ for the adsorption site at a certain pressure, and the replacement reaction occurs; the higher the partial pressure of HCHO, the stronger the replacement effect.